Many residential and commercial buildings include one or more remotely located thermostats for controlling the HVAC equipment used to heat, cool, control humidity, and/or ventilate the building. The thermostat typically monitors air temperature and/or other parameters within the building, and provides appropriate instructions to the HVAC equipment in order to control selected environmental parameters such as temperature and/or humidity within the building space.
Some thermostats are powered by electrical lines that extend between the thermostat and the HVAC equipment. Other thermostats rely on one or more batteries disposed within the thermostat to power the thermostat. Some thermostats have wired connections to the HVAC equipment, while others communicate with the HVAC equipment over a wireless connection.
It will be appreciated that when a thermostat loses power (e.g. via a battery failure) and/or loses communication with HVAC equipment (e.g. via battery failure and/or wireless connection failure), the thermostat will cease to provide the desired instructions to the HVAC equipment. This may cause conditions within the building to fall outside of desired environmental parameter levels. For example, if during a hot day, the thermostat ceases to provide the desired instructions to the HVAC equipment, the building interior may become excessively hot and/or humid. This may be problematic, particularly for people having increased sensitivity to heat. Also, excessive humidity, which if allowed to persist for a sufficient period of time, can cause mold and/or other damage to the building. Similarly, if during a cold day, the thermostat ceases to provide the desired instructions to the HVAC equipment, the building interior may become excessively cold, which under some circumstances, may cause pipes to freeze and/or cause other damage to the building.
A need exists, therefore, for an HVAC controller that can operate one or more pieces of HVAC equipment in accordance with instructions received from a properly operating thermostat, yet can also operate the HVAC equipment when communications between the thermostat and the HVAC controller are lost due to, for example, low battery power at the thermostat, malfunctioning thermostat sensor(s), malfunctioning communication and/or thermostat circuitry, electrical interference, and the like.